№37 Unified State Exam
When aluminum oxide reacted with nitric acid, a salt was formed. The salt was dried and calcined. The solid residue formed during calcination was subjected to electrolysis in molten cryolite. The metal obtained by electrolysis was heated with a concentrated solution containing potassium nitrate and potassium hydroxide, and a gas with a pungent odor was released. Write the equations for the reactions described.
Potassium chlorate was heated in the presence of a catalyst. The resulting salt was dissolved in water and subjected to electrolysis. A yellow-green gas was released at the anode, which was passed through a solution of sodium iodide. The simple substance formed as a result of this reaction reacted when heated with a solution of potassium hydroxide. Write the equations for the reactions described.
An iron plate was placed in a solution of copper (II) sulfate. At the end of the reaction, the plate was removed, and a barium nitrate solution was added dropwise to the resulting greenish solution until the formation of a precipitate stopped. The precipitate was filtered off, the solution was evaporated, and the remaining dry salt was calcined in air. This formed a solid brown substance, which was treated with concentrated hydroiodic acid. Write the equations for the reactions described.
The salt obtained by dissolving iron in hot concentrated sulfuric acid was treated with a solution of sodium hydroxide. The brown precipitate formed was filtered off and dried. The resulting substance was fused with iron. Write the equations for the reactions described.
Manganese (IV) oxide reacted with concentrated hydrochloric acid when heated. The released gas was passed through a solution of sodium hydroxide in the cold. The resulting solution was divided into two parts. Silver nitrate solution was added to one part of the solution, resulting in a white precipitate. A solution of potassium iodide was added to another part of the solution. As a result, a dark brown precipitate fell. Write down equations for the 4 reactions described.
Iron powder was dissolved in hydrochloric acid. Chlorine was passed through the resulting solution, as a result of which the solution acquired a yellowish color. Ammonium sulfide solution was added to this solution, resulting in a precipitate. The resulting precipitate was treated with a solution of sulfuric acid, and part of the precipitate dissolved. The undissolved part was yellow. Write the equations for the reactions described.
Alkalies were added to the aluminum-copper alloy. Carbon dioxide was passed through the resulting solution until the precipitation ceased. The precipitate was filtered and calcined, and the solid residue was fused with sodium carbonate. Write the equations for the reactions described.
Zinc chloride was dissolved in excess alkali. Carbon dioxide was passed through the resulting solution until the precipitation ceased. The precipitate was filtered and calcined, and the solid residue was calcined with coal. Write the equations for the reactions described.
Given a solution of the original salt, to which sodium hydroxide was added and heated, a gas with an irritating odor was released and a salt solution was formed, to which a dilute solution of hydrochloric acid was added, a gas with the smell of rotten eggs was released. If a solution of lead nitrate is added to a solution of the original salt, two salts are formed: one in the form of a black precipitate, the other salt is soluble in water. After removing the precipitate and calcining the filtrate, a mixture of two gases is formed, one of which is water vapor. Write the equations for the reactions described.
The iron was calcined in air. The resulting compound, in which iron is in two oxidation states, was dissolved in a strictly required amount of concentrated sulfuric acid. An iron plate was lowered into the solution and kept until its mass stopped decreasing. Then alkali was added to the solution, and a precipitate formed. Write the equations for the reactions described.
Some iron(II) sulfide was divided into two parts. One of them was treated with hydrochloric acid, and the other was fired in air. When the released gases interacted, a simple yellow substance was formed. The resulting substance was heated with concentrated sulfuric acid, and a brown gas was released. Write the equations for the reactions described.
Silicon was burned in a chlorine atmosphere. The resulting chloride was treated with water. The precipitate released was calcined. Then fused with calcium phosphate and coal. Write down equations for the reactions described.
The iron was burned in chlorine. The resulting salt was added to a solution of sodium carbonate, and a brown precipitate formed, which was filtered off and calcined. The resulting substance was dissolved in hydroiodic acid. Write the equations described reactions.
1) Copper nitrate was calcined, the resulting solid precipitate was dissolved in sulfuric acid. Hydrogen sulfide was passed through the solution, the resulting black precipitate was calcined, and the solid residue was dissolved by heating in concentrated nitric acid.
2) Calcium phosphate was fused with coal and sand, then the resulting simple substance was burned in an excess of oxygen, the combustion product was dissolved in an excess of caustic soda. A barium chloride solution was added to the resulting solution. The resulting precipitate was treated with excess phosphoric acid.
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Ca 3 (PO 4) 2 → P → P 2 O 5 → Na 3 PO 4 → Ba 3 (PO 4) 2 → BaHPO 4 or Ba(H 2 PO 4) 2 Ca 3 (PO 4) 2 + 5C + 3SiO 2 → 3CaSiO 3 + 2P + 5CO |
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3) Copper was dissolved in concentrated nitric acid, the resulting gas was mixed with oxygen and dissolved in water. Zinc oxide was dissolved in the resulting solution, then a large excess of sodium hydroxide solution was added to the solution.
4) Dry sodium chloride was treated with concentrated sulfuric acid at low heating, the resulting gas was passed into a solution of barium hydroxide. A solution of potassium sulfate was added to the resulting solution. The resulting sediment was fused with coal. The resulting substance was treated with hydrochloric acid.
5) A sample of aluminum sulfide was treated with hydrochloric acid. At the same time, gas was released and a colorless solution was formed. An ammonia solution was added to the resulting solution, and the gas was passed through a solution of lead nitrate. The resulting precipitate was treated with a solution of hydrogen peroxide.
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Al(OH) 3 ←AlCl 3 ←Al 2 S 3 → H 2 S → PbS → PbSO 4 Al 2 S 3 + 6HCl → 3H 2 S + 2AlCl 3 |
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6) Aluminum powder was mixed with sulfur powder, the mixture was heated, the resulting substance was treated with water, while gas was released and a precipitate formed, to which an excess of potassium hydroxide solution was added until complete dissolution. This solution was evaporated and calcined. An excess of hydrochloric acid solution was added to the resulting solid.
7) A solution of potassium iodide was treated with a solution of chlorine. The resulting precipitate was treated with a solution of sodium sulfite. First, a solution of barium chloride was added to the resulting solution, and after separating the precipitate, a solution of silver nitrate was added.
8) A gray-green powder of chromium (III) oxide was fused with an excess of alkali, the resulting substance was dissolved in water, and a dark green solution was obtained. Hydrogen peroxide was added to the resulting alkaline solution. A yellow solution was obtained, which turns orange when sulfuric acid is added. When hydrogen sulfide is passed through the resulting acidified orange solution, it becomes cloudy and turns green again.
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Cr 2 O 3 → KCrO 2 → K → K 2 CrO 4 → K 2 Cr 2 O 7 → Cr 2 (SO 4) 3 Cr 2 O 3 + 2KOH → 2KCrO 2 + H 2 O |
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9) Aluminum was dissolved in a concentrated solution of potassium hydroxide. Carbon dioxide was passed through the resulting solution until the precipitation ceased. The precipitate was filtered and calcined. The resulting solid residue was fused with sodium carbonate.
10) Silicon was dissolved in a concentrated solution of potassium hydroxide. Excess hydrochloric acid was added to the resulting solution. The cloudy solution was heated. The resulting precipitate was filtered and calcined with calcium carbonate. Write the equations for the reactions described.
11) Copper(II) oxide was heated in a stream of carbon monoxide. The resulting substance was burned in a chlorine atmosphere. The reaction product was dissolved in water. The resulting solution was divided into two parts. A solution of potassium iodide was added to one part, a solution of silver nitrate was added to the second. In both cases, the formation of a precipitate was observed. Write equations for the four reactions described.
12) Copper nitrate was calcined, the resulting solid was dissolved in dilute sulfuric acid. The solution of the resulting salt was subjected to electrolysis. The substance released at the cathode was dissolved in concentrated nitric acid. Dissolution proceeded with the release of brown gas. Write equations for the four reactions described.
13) Iron was burned in a chlorine atmosphere. The resulting substance was treated with an excess of sodium hydroxide solution. A brown precipitate formed, which was filtered and calcined. The residue after calcination was dissolved in hydroiodic acid. Write equations for the four reactions described.
14) Aluminum metal powder was mixed with solid iodine and a few drops of water were added. A solution of sodium hydroxide was added to the resulting salt until a precipitate formed. The resulting precipitate was dissolved in hydrochloric acid. Upon subsequent addition of sodium carbonate solution, precipitation was again observed. Write equations for the four reactions described.
15) As a result of incomplete combustion of coal, a gas was obtained, in the current of which iron(III) oxide was heated. The resulting substance was dissolved in hot concentrated sulfuric acid. The resulting salt solution was subjected to electrolysis. Write equations for the four reactions described.
16) A certain amount of zinc sulfide was divided into two parts. One of them was treated with nitric acid, and the other was fired in air. When the released gases interacted, a simple substance was formed. This substance was heated with concentrated nitric acid, and a brown gas was released. Write equations for the four reactions described.
17) Potassium chlorate was heated in the presence of a catalyst, and a colorless gas was released. By burning iron in an atmosphere of this gas, iron oxide was obtained. It was dissolved in excess hydrochloric acid. To the resulting solution was added a solution containing sodium dichromate and hydrochloric acid.
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1) 2KClO 3 → 2KCl + 3O 2 2) ЗFe + 2O 2 → Fe 3 O 4 3) Fe 3 O 4 + 8НІ → FeCl 2 + 2FeCl 3 + 4H 2 O 4) 6 FeCl 2 + Na 2 Cr 2 O 7 + 14 HCI → 6 FeCl 3 + 2 CrCl 3 + 2NaCl + 7H 2 O 18) Iron was burned in chlorine. The resulting salt was added to the sodium carbonate solution, and a brown precipitate formed. This precipitate was filtered and calcined. The resulting substance was dissolved in hydroiodic acid. Write equations for the four reactions described. 1) 2Fe + 3Cl 2 → 2FeCl 3 2)2FeCl 3 +3Na 2 CO 3 →2Fe(OH) 3 +6NaCl+3CO 2 3) 2Fe(OH) 3 Fe 2 O 3 + 3H 2 O 4) Fe 2 O 3 + 6HI → 2FeI 2 + I 2 + 3H 2 O |
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19) A solution of potassium iodide was treated with an excess of chlorine water, and first the formation of a precipitate was observed, and then its complete dissolution. The resulting iodine-containing acid was isolated from the solution, dried and carefully heated. The resulting oxide reacted with carbon monoxide. Write down the equations for the reactions described.
20) Chromium(III) sulfide powder was dissolved in sulfuric acid. At the same time, gas was released and a colored solution was formed. An excess of ammonia solution was added to the resulting solution, and the gas was passed through lead nitrate. The resulting black precipitate turned white after treatment with hydrogen peroxide. Write down the equations for the reactions described.
21) Aluminum powder was heated with sulfur powder, and the resulting substance was treated with water. The resulting precipitate was treated with an excess of a concentrated solution of potassium hydroxide until it was completely dissolved. A solution of aluminum chloride was added to the resulting solution and the formation of a white precipitate was again observed. Write down the equations for the reactions described.
22) Potassium nitrate was heated with powdered lead until the reaction stopped. The mixture of products was treated with water, and then the resulting solution was filtered. The filtrate was acidified with sulfuric acid and treated with potassium iodide. The isolated simple substance was heated with concentrated nitric acid. Red phosphorus was burned in the atmosphere of the resulting brown gas. Write down the equations for the reactions described.
23) Copper was dissolved in dilute nitric acid. An excess of ammonia solution was added to the resulting solution, observing first the formation of a precipitate, and then its complete dissolution with the formation of a dark blue solution. The resulting solution was treated with sulfuric acid until the characteristic blue color of copper salts appeared. Write down the equations for the reactions described.
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1)3Cu+8HNO 3 →3Cu(NO 3) 2 +2NO+4H 2 O 2)Cu(NO 3) 2 +2NH 3 H 2 O→Cu(OH) 2 + 2NH 4 NO 3 3)Cu(OH) 2 +4NH 3 H 2 O →(OH) 2 + 4H 2 O 4)(OH) 2 +3H 2 SO 4 → CuSO 4 +2(NH 4) 2 SO 4 + 2H 2 O |
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24) Magnesium was dissolved in dilute nitric acid, and no gas evolution was observed. The resulting solution was treated with an excess of potassium hydroxide solution while heating. The gas released was burned in oxygen. Write down the equations for the reactions described.
25) A mixture of potassium nitrite and ammonium chloride powders was dissolved in water and the solution was gently heated. The released gas reacted with magnesium. The reaction product was added to an excess of hydrochloric acid solution, and no gas evolution was observed. The resulting magnesium salt in solution was treated with sodium carbonate. Write down the equations for the reactions described.
26) Aluminum oxide was fused with sodium hydroxide. The reaction product was added to a solution of ammonium chloride. The released gas with a pungent odor is absorbed by sulfuric acid. The resulting medium salt was calcined. Write down the equations for the reactions described.
27) Chlorine reacted with a hot solution of potassium hydroxide. When the solution was cooled, crystals of Berthollet salt precipitated. The resulting crystals were added to a hydrochloric acid solution. The resulting simple substance reacted with metallic iron. The reaction product was heated with a new sample of iron. Write down the equations of the described reactions.
28) Copper was dissolved in concentrated nitric acid. An excess of ammonia solution was added to the resulting solution, observing first the formation of a precipitate, and then its complete dissolution. The resulting solution was treated with excess hydrochloric acid. Write down the equations for the reactions described.
29) Iron was dissolved in hot concentrated sulfuric acid. The resulting salt was treated with an excess of sodium hydroxide solution. The brown precipitate that formed was filtered and calcined. The resulting substance was fused with iron. Write equations for the four reactions described.
30) As a result of incomplete combustion of coal, a gas was obtained, in the current of which iron(III) oxide was heated. The resulting substance was dissolved in hot concentrated sulfuric acid. The resulting salt solution was treated with an excess of potassium sulfide solution.
31) A certain amount of zinc sulfide was divided into two parts. One of them was treated with hydrochloric acid, and the other was fired in air. When the released gases interacted, a simple substance was formed. This substance was heated with concentrated nitric acid, and a brown gas was released.
32) Sulfur was fused with iron. The reaction product was treated with hydrochloric acid. The gas released was burned in excess oxygen. The combustion products were absorbed by an aqueous solution of iron(III) sulfate.
Fe 2 (SO 4) 3 + 3K 2 S = 2FeS + S + 3K 2 SO 4
30. 2Fe + 3Cl 2 = 2FeCl 3
FeCl 3 + 3NaOH = Fe(OH) 3 + 3NaCl
2Fe(OH) 3 Fe 2 O 3 + 3H 2 O
Fe 2 O 3 + 6HI = 2FeI 2 + I 2 + 3H 2 O
31. Fe + 4HNO 3 (diluted) = Fe(NO 3) 3 + NO + 2H 2 O
(N 2 O and N 2 are also accepted as a product of the reduction of HNO 3)
2Fe(NO 3) 3 + 3Na 2 CO 3 + 3H 2 O = 2Fe(OH) 3 ↓ + 6NaNO 3 + 3CO 2
2HNO 3 + Na 2 CO 3 = 2NaNO 3 + CO 2 + H 2 O
2Fe(OH) 3 Fe 2 O 3 + 3H 2 O
Fe 2 O 3 + 2Al 2Fe + Al 2 O 3
FeS + 2HCl = FeCl 2 + H 2 S
FeCl 2 + 2KOH = Fe(OH) 2 ↓ + 2KCl
Fe(OH) 2 FeO + H 2 O
33. 2Fe + 3Cl 2 = 2FeCl 3
2FeCl 3 + 2KI = 2FeCl 2 + I 2 + 2KCl
3I 2 + 10HNO 3 = 6HIO 3 + 10NO + 2H 2 O
34. Fe + 2HCl = FeCl 2 + H 2
FeCl 2 + 2NaOH = Fe(OH) 2 ↓ + 2NaCl
4Fe(OH) 2 + 2H 2 O + O 2 = 4Fe(OH) 3 ↓
Fe(OH) 3 + 6HI = 2FeI 2 + I 2 + 6H 2 O
35. Fe 2 (SO 4) 3 + 3Ba(NO 3) 2 = 3BaSO 4 ↓ + 2Fe(NO 3) 3
Fe(NO 3) 3 + 3NaOH = Fe(OH) 3 ↓ + 3NaNO 3
2Fe(OH) 3 Fe 2 O 3 + 3H 2 O
Fe 2 O 3 + 6HCl 2FeCl 3 + 3H 2 O
Zinc. Zinc compounds.
Zinc – quite active metal, but it is stable in air, since it is covered with a thin layer of oxide, which protects it from further oxidation. When heated, zinc reacts with simple substances(exception is nitrogen):
2Zn + О 2 2ZnО
Zn + Cl 2 ZnCl 2
3Zn + 2P Zn 3 P 2
as well as with non-metal oxides and ammonia:
3Zn + SO 2 2ZnO + ZnS
Zn + CO 2 ZnO + CO
3Zn + 2NH 3 Zn 3 N 2 + 3H 2
When heated, zinc oxidizes under the action of water vapor:
Zn + H 2 O (steam) ZnO + H 2
Zinc reacts with solutions of sulfuric and hydrochloric acids, displacing hydrogen from them:
Zn + 2HCl = ZnCl 2 + H 2
Zn + H 2 SO 4 = ZnSO 4 + H 2
How the active metal zinc reacts with oxidizing acids:
Zn + 2H 2 SO 4 (conc.) = ZnSO 4 + SO 2 + 2H 2 O
4Zn + 5H 2 SO 4 (conc.) = 4ZnSO 4 + H 2 S + 4H 2 O
Zn + 4HNO 3(conc.) → Zn(NO 4) 2 + 2NO 2 + 2H 2 O
4Zn + 10HNO 3(ultra dil.) = 4Zn(NO 3) 2 + NH 4 NO 3 + 3H 2 O
When zinc is fused with alkalis, zincate is formed:
Zn + 2NaOH (crystal) Na 2 ZnO 2 + H 2
Zinc dissolves well in alkali solutions:
Zn + 2KOH + 2H 2 O = K 2 + H 2
Unlike aluminum, zinc also dissolves in an aqueous solution of ammonia:
Zn + 4NH 3 + 2H 2 O = (OH) 2 + H 2
Zinc reduces many metals from solutions of their salts:
CuSO 4 + Zn = Zn SO 4 + Cu
Pb(NO 3) 2 + Zn = Zn(NO 3) 2 + Pb
4Zn + KNO 3 + 7KOH = NH 3 + 4K 2 ZnO 2 + 2H 2 O
4Zn + 7NaOH + 6H 2 O + NaNO 3 = 4Na 2 + NH 3
3Zn + Na 2 SO 3 + 8HCl = 3ZnCl 2 + H 2 S + 2NaCl + 3H 2 O
Zn + NaNO 3 + 2HCl = ZnCl 2 + NaNO 2 + H 2 O
II. Zinc compounds (zinc compounds are poisonous).
1) Zinc oxide.
Zinc oxide has amphoteric properties.
ZnO + 2HCl = ZnCl 2 + H 2 O
ZnO + 2NaOH Na 2 ZnO 2 + H 2 O
ZnO + Na 2 O Na 2 ZnO 2
ZnO + SiO 2 ZnSiO 3
ZnO + BaCO 3 BaZnO 2 + CO 2
Zinc is reduced from oxides by the action of strong reducing agents:
ZnO + C (coke) Zn + CO
ZnO + CO Zn + CO 2
2) Zinc hydroxide.
Zinc hydroxide has amphoteric properties.
Zn(OH) 2 + 2HCl = ZnCl 2 + 2H 2 O
Zn(OH) 2 + 2NaOH Na 2 ZnO 2 + 2H 2 O
Zn(OH) 2 + 2NaOH = Na 2
2Zn(OH) 2 + CO 2 = (ZnOH) 2 CO 3 + H 2 O
Zn(OH) 2 + 4(NH 3 H 2 O) = (OH) 2
Zinc hydroxide is thermally unstable:
Zn(OH) 2 ZnO + H 2 O
3) Salt.
CaZnO 2 + 4HCl (excess) = CaCl 2 + ZnCl 2 + 2H 2 O
Na 2 ZnO 2 + 2H 2 O = Zn(OH) 2 + 2NaHCO 3
Na 2 + 2CO 2 = Zn(OH) 2 + 2NaHCO 3
2ZnSO 4 2ZnO + 2SO 2 + O 2
ZnS + 4H 2 SO 4 (conc.) = ZnSO 4 + 4SO 2 + 4H 2 O
ZnS + 8HNO 3 (conc.) = ZnSO 4 + 8NO 2 + 4H 2 O
ZnS + 4NaOH + Br 2 = Na 2 + S + 2NaBr
Zinc. Zinc compounds.
1. Zinc oxide was dissolved in a solution of hydrochloric acid and the solution was neutralized by adding sodium hydroxide. Released gelatinous substance white separated and treated with an excess of alkali solution, and the precipitate was completely dissolved. neutralization of the resulting solution with an acid, for example, nitric acid, leads to the re-formation of a gelatinous precipitate. Write the equations for the reactions described.
2. Zinc was dissolved in very dilute nitric acid and excess alkali was added to the resulting solution, obtaining a clear solution. Write the equations for the reactions described.
3. The salt obtained by reacting zinc oxide with sulfuric acid was calcined at a temperature of 800°C. The solid reaction product was treated with a concentrated alkali solution, and carbon dioxide was passed through the resulting solution. Write the equations for the reactions described.
4. Zinc nitrate was calcined, and the reaction product was treated with sodium hydroxide solution when heated. Carbon dioxide was passed through the resulting solution until the precipitation ceased, after which it was treated with an excess of concentrated ammonia, and the precipitate dissolved. Write the equations for the reactions described.
5. Zinc was dissolved in very dilute nitric acid, the resulting solution was carefully evaporated and the residue was calcined. The reaction products were mixed with coke and heated. Write the equations for the reactions described.
6. Several zinc granules were dissolved by heating in a solution of sodium hydroxide. Nitric acid was added to the resulting solution in small portions until a precipitate formed. The precipitate was separated, dissolved in dilute nitric acid, the solution was carefully evaporated and the residue was calcined. Write the equations for the reactions described.
7. Zinc metal was added to concentrated sulfuric acid. the resulting salt was isolated, dissolved in water, and barium nitrate was added to the solution. After separating the precipitate, magnesium shavings were added to the solution, the solution was filtered, the filtrate was evaporated and calcined. Write the equations for the reactions described.
8. Zinc sulfide was calcined. The resulting solid reacted completely with the potassium hydroxide solution. Carbon dioxide was passed through the resulting solution until a precipitate formed. The precipitate was dissolved in hydrochloric acid. Write the equations for the reactions described.
9. A quantity of zinc sulfide was divided into two parts. One of them was treated with hydrochloric acid, and the other was fired in air. During the interaction of the evolved gases, a simple substance was formed. This substance was heated with concentrated nitric acid, and a brown gas was released. Write the equations for the reactions described.
10. Zinc was dissolved in a solution of potassium hydroxide. The released gas reacted with lithium, and hydrochloric acid was added dropwise to the resulting solution until precipitation stopped. It was filtered and calcined. Write the equations for the reactions described.
1) ZnO + 2HCl = ZnCl 2 + H 2 O
ZnCl 2 + 2NaOH = Zn(OH) 2 ↓ + 2NaCl
Zn(OH) 2 + 2NaOH = Na 2
Na 2 + 2HNO 3 (deficiency) = Zn(OH) 2 ↓ + 2NaNO 3 + 2H 2 O
2) 4Zn + 10HNO 3 = 4Zn(NO 3) 2 + NH 4 NO 3 + 3H 2 O
HNO 3 + NaOH = NaNO 3 + H 2 O
NH 4 NO 3 + NaOH = NaNO 3 + NH 3 + H 2 O
Zn(NO 3) 2 + 4NaOH = Na 2 + 2NaNO 3
3) ZnO + H 2 SO 4 = ZnSO 4 + H 2 O
2ZnSO 4 2ZnO + 2SO 2 + O 2
ZnO + 2NaOH + H 2 O = Na 2
4) 2Zn(NO 3) 2 2ZnO + 4NO 2 + O 2
ZnO + 2NaOH + H 2 O = Na 2
Na 2 + 2CO 2 = Zn(OH) 2 ↓ + 2NaHCO 3
Zn(OH) 2 + 4(NH 3 H 2 O) = (OH) 2 + 4H 2 O
5) 4Zn + 10HNO 3 = 4Zn(NO 3) 2 + NH 4 NO 3 + 3H 2 O
2Zn(NO 3) 2 2ZnO + 4NO 2 + O 2
NH 4 NO 3 N 2 O + 2H 2 O
ZnO + C Zn + CO
6) Zn + 2NaOH + 2H 2 O = Na 2 + H 2
Na 2 + 2HNO 3 = Zn(OH) 2 ↓ + 2NaNO 3 + 2H 2 O
Zn(OH) 2 + 2HNO 3 = Zn(NO 3) 2 + 2H 2 O
2Zn(NO 3) 2 2ZnO + 4NO 2 + O 2
7) 4Zn + 5H 2 SO 4 = 4ZnSO 4 + H 2 S + 4H 2 O
ZnSO 4 + Ba(NO 3) 2 = Zn(NO 3) 2 + BaSO 4
Zn(NO 3) 2 + Mg = Zn + Mg(NO 3) 2
2Mg(NO 3) 2 2Mg(NO 2) 2 + O 2
8) 2ZnS + 3O 2 = 2ZnO + 2SO 2
ZnO + 2NaOH + H 2 O = Na 2
Na 2 + CO 2 = Zn(OH) 2 + Na 2 CO 3 + H 2 O
Zn(OH) 2 + 2HCl = ZnCl 2 + 2H 2 O
9) ZnS + 2HCl = ZnCl 2 + H 2 S
2ZnS + 3O 2 = 2ZnO + 2SO 2
2H 2 S + SO 2 = 3S + 2H 2 O
S + 6HNO 3 = H 2 SO 4 + 6NO 2 + 2H 2 O
10) Zn + 2KOH + 2H 2 O = K 2 + H 2
H2 + 2Li = 2LiH
K 2 + 2HCl = 2KCl + Zn(OH) 2 ↓
Zn(OH) 2 ZnO + H 2 O
Copper and copper compounds.
Copper is a chemically low-active metal; it does not oxidize in dry air and at room temperature, but in humid air, in the presence of carbon monoxide (IV), it becomes covered with a green coating of hydroxycopper (II) carbonate.
2Cu + H2O + CO2 = (CuOH)2CO3
When heated, copper reacts with sufficient strong oxidizing agents,
with oxygen, forming CuO, Cu 2 O depending on the conditions:
4Cu + O 2 2Cu 2 O 2Cu + O 2 2CuO
With halogens, sulfur:
Cu + Cl 2 = CuCl 2
Сu + Br 2 = CuBr 2
Copper dissolves in oxidizing acids:
when heated in concentrated sulfuric acid:
Cu + 2H 2 SO 4 (conc.) CuSO 4 + SO 2 + 2H 2 O
without heating in nitric acid:
Cu + 4HNO 3(conc.) = Cu(NO 3) 2 + 2NO 2 + 2H 2 O
3Cu + 8HNO 3(dissolved..) = 3Cu(NO 3) 2 + 2NO + 4H 2 O
3Cu + 2HNO3 + 6HCl = 3CuCl2 + 2NO + 4H2O
Copper is oxidized by nitrogen oxide (IV) and iron salts (III)
2Cu + NO 2 = Cu 2 O + NO
2FeCl 3 + Cu = 2FeCl 2 + CuCl 2
Copper displaces metals to the right in the voltage series from solutions of their salts:
Hg(NO 3) 2 + Cu = Cu(NO 3) 2 + Hg
II. Copper compounds.
1) Oxides.
Copper(II) oxide
In the laboratory, copper (II) oxide is obtained by oxidation of copper when heated, or by calcination (CuOH) 2 CO 3, Cu(NO 3) 2:
(CuOH) 2 CO 3 2CuO + CO 2 + H 2 O
2Cu(NO 3) 2 2CuO + 4NO 2 + O 2
Copper oxide exhibits weakly expressed amphoteric properties ( with a predominance of the main). CuO interacts with acids:
СuO + 2HBr = CuBr 2 + H 2 O
CuO + 2HCl = CuCl 2 + H 2 O
CuO + 2H + = Cu 2+ + H 2 O
3CuO + 2NH 3 3Cu + N 2 + 3H 2 O
СuO + C = Cu + CO
3CuO + 2Al = 3Cu + Al 2 O 3
Copper(I) oxide
In the laboratory it is obtained by reducing freshly precipitated copper (II) hydroxide, for example, with aldehydes or glucose:
CH 3 CHO + 2Cu(OH) 2 CH 3 COOH + Cu 2 O↓ + 2H 2 O
CH 2 OH (CHOH) 4 CHO + 2Cu(OH) 2 CH 2 OH (CHOH) 4 COOH + Cu 2 O↓ + 2H 2 O
Copper(I) oxide has main properties. When copper (I) oxide is treated with hydrohalic acid, copper (I) halides and water are obtained:
Cu 2 O + 2HCl = 2CuCl↓ + H 2 O
When Cu 2 O is dissolved in oxygen-containing acids, for example, in sulfuric solution, copper (II) salts and copper are formed:
Cu 2 O + H 2 SO 4 (diluted) = CuSO 4 + Cu + H 2 O
In concentrated sulfuric and nitric acids, only salts (II) are formed.
Cu 2 O + 3H 2 SO 4 (conc.) = 2CuSO 4 + SO 2 + 3H 2 O
Cu 2 O + 6HNO 3 (conc.) = 2Cu(NO 3) 2 + 2NO 2 + 3H 2 O
5Cu2O + 13H2SO4 + 2KMnO4 = 10CuSO4 + 2MnSO4 + K2SO4 + 13H2O
Stable copper (I) compounds are insoluble compounds (CuCl, Cu 2 S) or complex compounds +. The latter are obtained by dissolving copper (I) oxide, copper (I) chloride in a concentrated solution of ammonia:
Cu 2 O + 4NH 3 + H 2 O = 2OH
CuCl + 2NH 3 = Cl
Ammonia solutions of copper (I) salts interact with acetylene:
СH ≡ CH + 2Cl → Сu–C ≡ C–Cu + 2NH 4 Cl
In redox reactions, copper (I) compounds exhibit redox duality
Cu 2 O + CO = 2Cu + CO 2
Cu 2 O + H 2 = 2Cu + H 2 O
3Cu 2 O + 2Al = 6Cu + Al 2 O 3
2Cu2O + O2 = 4CuO
2) Hydroxides.
Copper(II) hydroxide.
Copper (II) hydroxide exhibits weakly pronounced amphoteric properties (with a predominance of main). Cu (OH) 2 interacts with acids:
Cu(OH) 2 + 2HBr = CuBr 2 + 2H 2 O
Cu(OH) 2 + 2HCl = CuCl 2 + 2H 2 O
Cu(OH) 2 + 2H + = Cu 2+ + 2H 2 O
Copper (II) hydroxide easily interacts with an ammonia solution, forming a blue-violet complex compound:
Сu(OH) 2 + 4(NH 3 H 2 O) = (OH) 2 + 4H 2 O
Cu(OH) 2 + 4NH 3 = (OH) 2
When copper (II) hydroxide interacts with concentrated (more than 40%) alkali solutions, a complex compound is formed:
Cu(OH) 2 + 2NaOH (conc.) = Na 2
When heated, copper(II) hydroxide decomposes:
Сu(OH) 2 CuO + H 2 O
3) Salt.
Copper (I) salts.
In redox reactions, copper (I) compounds exhibit redox duality. As reducing agents they react with oxidizing agents:
CuCl + 3HNO 3(conc.) = Cu(NO 3) 2 + HCl + NO 2 + H 2 O
2CuCl + Cl 2 = 2CuCl 2
4CuCl + O 2 + 4HCl = 4CuCl 2 + 2H 2 O
2CuI + 4H 2 SO 4 + 2MnO 2 = 2CuSO 4 + 2MnSO 4 + I 2 + 4H 2 O
4CuI + 5H 2 SO 4 (conc. hor.) = 4CuSO 4 + I 2 + H 2 S + 4H 2 O
Cu 2 S + 8HNO 3 (conc. cold) = 2Cu(NO 3) 2 + S + 4NO 2 + 4H 2 O
Cu 2 S + 12HNO 3 (conc. cold) = Cu (NO 3) 2 + CuSO 4 + 10NO 2 + 6H 2 O
For copper (I) compounds, a disproportionation reaction is possible:
2CuCl = Cu + CuCl 2
Complex connections type + is obtained by dissolving in a concentrated ammonia solution:
CuCl + 3NH 3 + H 2 O → OH + NH 4 Cl
Copper(II) salts
In redox reactions, copper (II) compounds exhibit oxidizing properties:
2CuCl 2 + 4KI = 2CuI + I 2 + 4HCl
2CuCl 2 + Na 2 SO 3 + 2NaOH = 2CuCl + Na 2 SO 4 + 2NaCl + H 2 O
5CuBr 2 + 2KMnO 4 + 8H 2 SO 4 = 5CuSO 4 + K 2 SO 4 + 2MnSO 4 + 5Br 2 + 8H 2 O
2CuSO 4 + Na 2 SO 3 + 2H 2 O = Cu 2 O + Na 2 SO 4 + 2H 2 SO 4
CuSO 4 + Fe = FeSO 4 + Cu
CuS + 8HNO 3 (conc. hor..) = CuSO 4 + 8NO 2 + 4H 2 O
CuS + 2FeCl 3 = CuCl 2 + 2FeCl 2 + S
2CuS + 3O 2 2CuO + 2SO 2
CuS + 10HNO 3(conc.) = Cu(NO 3) 2 + H 2 SO 4 + 8NO 2 + 4H 2 O
2CuCl 2 + 4KI = 2CuI + I 2 ↓ + 4KCl
CuBr 2 + Na 2 S = CuS↓ + 2NaBr
Cu(NO 3) 2 + Fe = Fe(NO 3) 2 + Cu
CuSO 4 + Cu + 2NaCl = 2CuCl↓ + Na 2 SO 4
2Cu(NO 3) 2 + 2H 2 O 2Cu + O 2 + 4HNO 3
CuSO 4 + 2NaOH = Cu(OH) 2 ↓ + Na 2 SO 4
Master class in chemistry for students in grades 10-11 in the city to prepare for the Unified State Exam
Lesson No. 1
Topic: "Redox reactions in"
Plan of implementation.
General idea of OVR
a) definition of the essence of OVR
b) classification of ORR: intermolecular, intramolecular, disproportionation
c) oxidation, oxidizing agent, reduction, reducing agent.
The most important oxidizing and reducing agents. Dependence of ORR products on the reaction environment
a) using the example of potassium permanganate
b) chromium compounds
Features of the interaction of nitric acid with metals:
a) depending on the acid concentration
b) depending on the activity of the metal
Arrangement of coefficients in OVR using the electronic balance method.
M B O U S O SH No. 1
Lesson No. 2
Topic: "Solving problems of increased complexity"
Plan of implementation.
Messages about the introduction of tasks on a mixture into the C4KIM task Drawing up an algorithm for solving problems on a mixture, consisting of two or three components Solving problems based on the compilation of an algorithm Drawing up an algorithm for solving problems if amphoteric compounds are specified in the conditions Solving problems using this algorithm Analysis of tasks related to qualitative reactions chemical compounds by their properties (C2)
M B O U S O SH No. 1
Mixture problems (C4)
Task No. 1
A mixture of zinc and magnesium, weighing 15.4 g, was subjected to oxidation. As a result, a mixture of oxides of these metals with a mass of 20.2 g was formed. Determine the mass fractions of metals in the initial mixture.
Task No. 2
A mixture of magnesium and iron weighing 0.4 g was treated with hydrochloric acid. As a result, gas (n.a.) with a volume of 0.224 liters was released. Determine the mass fractions of metals in the mixture.
Task No. 3
A mixture of copper, iron, aluminum weighing 8.7 g was treated with a solution of hydrochloric acid. Gas (n.o.) with a volume of 4.48 liters was released. The same mixture was treated with concentrated nitric acid, as a result, a brown gas with a volume of 2.24 liters was released. (Well.). Determine the mass fractions of metals in the initial mixture.
Task No. 4
To completely dissolve the mixture of copper and copper oxide, 80 g of 63% nitric acid was required, while 6.72 liters (n.a.) of brown gas were released. Calculate the mass fractions (%) of substances in the original mixture.
Problem No. 5
To completely dissolve the mixture of aluminum and aluminum oxide, 320 g of a 10% sodium hydroxide solution was required, while 10.08 liters (n.a.) of gas were released. Determine the mass fractions (in%) of substances in the initial mixture.
Tasks for C2
Task No. 1
As a result of incomplete combustion of coal, a gas was obtained, in the flow of which iron oxide (III) was heated. The resulting substance was dissolved in hot concentrated sulfuric acid. The resulting solution was subjected to electrolysis. Write equations for the four reactions described.
Task No. 2
A certain amount of zinc sulfide was divided into two parts. One of them was treated with nitric acid, and the other was fired in air. When the released gases interacted, a simple substance was formed. This substance was heated with concentrated nitric acid, and a brown gas was released. Write equations for the four reactions described.
Task No. 3
Metallic aluminum powder was mixed with solid iodine and a few drops of water were added. A solution of sodium hydroxide was added to the resulting salt until a precipitate formed. The resulting precipitate was dissolved in hydrochloric acid. Upon subsequent addition of sodium carbonate solution, precipitation was again observed. Write equations for the four reactions described.
Task No. 4
Zinc turnings were dissolved in a solution of potassium hydroxide. Excess sulfur dioxide was passed through the resulting solution. The precipitate formed was calcined, and the resulting product was dissolved in an excess of sulfuric acid. Write down the reaction equations.
1) Silicon was burned in a chlorine atmosphere. The resulting chloride was treated with water. The precipitate released was calcined. Then it was fused with calcium phosphate and coal. Write down equations for the four reactions described.
2) The gas obtained by treating calcium nitride with water was passed over hot powder of copper(II) oxide. The solid thus obtained was dissolved in concentrated nitric acid, the solution was evaporated, and the resulting solid residue was calcined. Write down equations for the four reactions described.
3) A certain amount of iron(II) sulfide was divided into two parts. One of them was treated with hydrochloric acid, and the other was fired in air. When the released gases interacted, a simple substance was formed yellow color. The resulting substance was heated with concentrated nitric acid, and a brown gas was released. Write equations for the four reactions described.
4) When aluminum oxide interacts with nitric acid, a salt is formed. The salt was dried and calcined. The solid residue formed during calcination was subjected to electrolysis in molten cryolite. The metal obtained by electrolysis was heated with a concentrated solution containing potassium nitrate and potassium hydroxide, and a gas with a pungent odor was released. Write equations for the four reactions described.
5) Chromium(VI) oxide reacted with potassium hydroxide. The resulting substance was treated with sulfuric acid, and an orange salt was isolated from the resulting solution. This salt was treated with hydrobromic acid. The resulting simple substance reacted with hydrogen sulfide. Write equations for the four reactions described.
6) Magnesium powder was heated in a nitrogen atmosphere. When the resulting substance interacted with water, a gas was released. The gas was passed through an aqueous solution of chromium(III) sulfate, resulting in the formation of a gray precipitate. The precipitate was separated and treated by heating with a solution containing hydrogen peroxide and potassium hydroxide. Write equations for the four reactions described.
7) Ammonia was passed through hydrobromic acid. A solution of silver nitrate was added to the resulting solution. The precipitate that formed was separated and heated with zinc powder. The metal formed during the reaction was exposed to a concentrated solution of sulfuric acid, which released a gas with a pungent odor. Write equations for the four reactions described.
8) Potassium chlorate was heated in the presence of a catalyst, and a colorless gas was released. By burning iron in an atmosphere of this gas, iron oxide was obtained. It was dissolved in excess hydrochloric acid. To the resulting solution was added a solution containing sodium dichromate and hydrochloric acid. Write equations for the four reactions described.
9) Sodium was heated in a hydrogen atmosphere. When water was added to the resulting substance, gas evolution and the formation of a clear solution were observed. Brown gas was passed through this solution, which was obtained as a result of the interaction of copper with a concentrated solution of nitric acid. Write equations for the four reactions described.
10) Aluminum reacted with a solution of sodium hydroxide. The released gas was passed over heated copper(II) oxide powder. The resulting simple substance was dissolved by heating in concentrated sulfuric acid. The resulting salt was isolated and added to the potassium iodide solution. Write equations for the four reactions described.
11) Conducted electrolysis of a sodium chloride solution. Iron(III) chloride was added to the resulting solution. The precipitate that formed was filtered and calcined. The solid residue was dissolved in hydroiodic acid. Write equations for the four reactions described.
12) Aluminum powder was added to the sodium hydroxide solution. Excess carbon dioxide was passed through the solution of the resulting substance. The precipitate that formed was separated and calcined. The resulting product was fused with sodium carbonate. Write equations for the four reactions described.
